ES2385137T3 - Control cylinder comprising brake fluid injection means in said control cylinder, and braking system comprising such a control cylinder - Google Patents

Abstract

The present invention relates mainly to a braking system comprising a master cylinder comprising means of connection to a hydraulic braking circuit and means of connecting at least one chamber of the master cylinder to means of injecting brake fluid into said chamber. The main subject of the invention is a master cylinder (48) comprising at least one variable-volume chamber and one moving piston (207), the movement of which causes the volume of said chamber to vary, and means of connecting said chamber to a hydraulic braking circuit, characterized in that it further comprises means (217) of connection to a source (116) of pressurized brake fluid. The invention applies notably to the motor industry. The invention applies mainly to the braking industry.

Description

Control cylinder comprising brake fluid injection means in said control cylinder, and braking system comprising such a control cylinder.

The present invention relates mainly to a braking system consisting of a control cylinder comprising connection means to a hydraulic brake circuit and connection means of at least one chamber of the control cylinder to the liquid injection means of brakes in the aforementioned chamber.

It is known to manufacture brake assist servomotors (brake boosters) that exert a force on a push rod of a control cylinder that is an increasing function of the force exerted by the driver on a control rod, through a pedal brake and as described in GB 2 170285.

It is also known to implement a pedal sensation simulator connected to a pedal equipped with brake setpoint sensors associated with a servomotor that executes the setpoints mentioned. At the cost of increasing complexity and fragility, the devices in the simulator allow a decoupling between the position of a brake pedal and the hydraulic pressure available in the braking circuits. Also, WO 2007 080106 and WO 2007 080158, which are incorporated in the present patent application as a reference, describe pneumatic brake booster servo motors with decoupling between the control rod and the pushrod.

The present invention aims to offer a braking system that implements a control cylinder that allows decoupling between the brake pedal and the pressure existing in the braking circuit fed by said control cylinder that has great robustness and simplicity. of realization.

The present invention also has the purpose of offering a braking system that has a particularly pleasant brake pedal to use for the driver, that is to say that it has a much requested pedal feel.

The present invention also has the purpose of offering the braking system consisting of a braking assistance device, but which allows effective braking in the event that this device does not work.

These objectives are achieved, according to the present invention, by injecting, under control, brake fluid into at least one of the control cylinder chambers.

A subject of the invention is a control cylinder consisting of at least one variable volume chamber and a mobile piston, whose displacement causes the volume of said chamber and of the means for connecting said chamber to a hydraulic braking circuit to vary. , characterized in that it also comprises connection means to a source of pressurized brake fluid.

A subject of the invention is also a control cylinder characterized in that said means for connecting to a source of pressurized brake fluid flow directly into said variable volume chamber.

A subject of the invention is also a control cylinder characterized in that it consists of a feedback chamber and in that the said means of connection to a source of high pressure brake fluid flow into said feedback chamber.

The invention also has a braking system characterized in that it consists of a control cylinder, a source of pressurized brake fluid connected by said connection means to said said variable volume chamber of said control cylinder and control means of supply of said variable volume chamber with the pressurized brake fluid.

A subject of the invention is also a braking system characterized in that it also includes hydraulic braking assistance means.

A subject of the invention is also a braking system characterized in that it includes means for connecting the source of pressurized brake fluid to a thrust chamber of said hydraulic braking assistance means.

A subject of the invention is also a braking system characterized in that it also includes hermetically insulated means, under control, of said variable volume chamber of said control cylinder with respect to said source of pressurized brake fluid.

A subject of the invention is also a system characterized in that said source of pressurized brake fluid includes a control cylinder consisting of a variable volume chamber and a piston driven, under control, by a motor.

A subject of the invention is also a braking system characterized in that said control cylinder of the pressurized brake fluid source is a tandem control cylinder consisting of:

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a first chamber connected by means of connection to said chamber of said control cylinder including means of connection to a hydraulic circuit, and

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a second variable volume chamber connected by a connection to said hydraulic braking assistance means.

A subject of the invention is also a braking system characterized in that said control cylinder of said pressurized brake fluid source consists of two chambers having two different diameters and because these include means that transfer the means securing the variation of the internal volumes of the aforementioned variable volume chambers of said control cylinder.

The present invention will be better understood through the following description and the attached figures provided as non-limiting examples and among which:

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Figure 1 is a schematic sectional view illustrating a first embodiment of a system according to the present invention;

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Figure 2 is a schematic sectional view of a second embodiment of a braking system according to the present invention;

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Figure 3 is a sectional view of a third embodiment of the braking system according to the present invention;

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Figure 4 is a schematic sectional view of a fourth embodiment of the device according to the present invention;

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Figure 5 is a sectional view of a fifth embodiment of a braking system according to the present invention;

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Figure 6 is a sectional view, on a larger scale, of the brake fluid injection means implemented in the system of Figure 5.

In Figures 1 to 6 the same references are used to designate the same elements.

In Figure 1, a braking system consisting of a brake pedal 1 that moves a control rod 36 can be seen, which in turn pushes on a brake booster 72. The brake assist servomotor 72 exerts a force on a push rod amplified by the brake assist servomotor 72.

The servomotor 72 is, for example, a pneumatic servomotor for braking assistance, a hydraulic servomotor for braking assistance, an electric servomotor for braking assistance or others. Normally, the servomotor 72 is equipped with a reaction device, usually an incompressible elastomer reaction disk that transmits to the control rod 36 a part of the reaction to the thrust exerted on the push rod 47.

Push rod 47 pushes, under control, on a primary piston 207 of a control cylinder 48. In the advantageous example illustrated, the control cylinder 48 is a tandem control cylinder, with feedback from a feedback chamber between two cup joints and feedback holes located in the piston. However, the implementation of other types of control cylinders, such as, for example, single-control cylinders (of a single chamber), or of a number of chambers greater than 2, does not go beyond the scope of the present invention. Likewise, the implementation of control cylinders with valves or the like is not beyond the scope of the present invention.

A brake fluid reservoir 98 feeds directly, by gravity flow or indirectly, the control cylinder chambers 48. The control cylinder 48 further comprises connection means to a hydraulic braking circuit that includes brakes equipped with hydraulic pistons.

Preferably, the system according to the present invention further includes a sensor 66 that detects the brake setpoints 65 transmitted to a computer 5 (ECU in Anglo-Saxon terminology). The computer 5 also receives a signal 19 from other sensors, especially pressure sensors or other computers in the vehicle. The computer 5 transmits a control signal 100 to a source 116 of pressurized brake fluid. In a first variant embodiment, not illustrated, the brake assist servomotor 72 transmits, on the pushrod 47, a force that is an increasing function of the force exerted by the rod 36. The relationship between the force exerted by the rod 36 on the assistive servomotor 72 and the force exerted by this servomotor 72 on the pushrod 47 is called the assistance ratio. The assistance ratio is constant for low-pressure braking and increases, preferably for high-pressure braking that corresponds to emergency braking by implementing a device called emergency braking assistance (or brake assist in Anglo-Saxon terminology).

In the illustrated example, the computer 5 is also connected by a control connection 100 'to the brake assist servo motor 72, the assistance force being exerted by the servomotor 72 according to a setpoint 100' produced by the computer 5 as a function of the signal 65 transmitted by sensor 66 and / or signal 19.

The pressure source is connected via a connection 213 to one of the chambers, for example, as illustrated, to the primary chamber of the control cylinder 48.

The source 116 ensures the pre-filling and / or the filling of the primary chamber of the control cylinder 48 allowing the operation of the active modes, ie without needing the support on the pedal 1 of the braking system, for example for braking automatic under the control of a radar (ACC), parking braking or others.

The increase in pressure in the primary chamber of the control cylinder 48 pushes the secondary piston which in turn ensures the pressure rise in the secondary circuit.

On the other hand, in the normal braking mode, that is, the result of the fact that the driver rests his foot on pedal 1, it is possible, according to the invention, to inject a volume of liquid into the primary and / or secondary chamber of the control cylinder 48 shortening the pedal travel obtained, and this shortening of the pedal travel in normal operation allows to select a control cylinder of reduced diameter which, in the absence of the device according to the present invention, would result in a pedal travel too long for Be accepted by the user. However, the decrease in the diameter of the control cylinder is masked by the injection of brake fluid into the primary and / or secondary chamber of the control cylinder 48. For example, control cylinders 48 having a diameter between 2 can be used and 50 mm preferably between 10 mm and 40 mm and still more preferably between 19.6 mm and 33 mm, for example equal to 22.2 mm, 23.8 mm or 25.4 mm.

The decrease in the diameter of the control cylinder with the same pedal travel, or even a decreased pedal travel so that the driver's comfort increases during normal braking, also allows the brake pressure to be increased for a force of application on pedal 1 given in case of failure of the pressure source 116. It should be noted that the case of a fault like this, with a small diameter control cylinder, is resolved by an increase in the path of the faulty pedal (which it cannot be masked in any way in the absence of injection of brake fluid in the primary and / or secondary chamber of the control cylinder 48). However, this increase in pedal travel will be entirely acceptable to the extent that it is exceptional (only in case of failure of the pressure source 116) and that improves braking efficiency (particularly for drivers unable to exert a force too big on the brake pedal, especially for the elderly and some women).

Likewise, the present invention is especially interesting for hybrid vehicles consisting of a thermal motor and an electric motor capable of functioning as a generator that recharges the batteries during braking. Indeed, the regenerative braking of the electric motor operating as a generator must be completed so that the desired braking is obtained. Thus, an active braking can correspond to this braking complement even allowing a normal pedal sensation, the control rod 36 and the push rod 47 being disengaged by an injection of brake fluid into the thrust chamber 76.

In the case where the servomotor 72 is a hydraulic brake assist servomotor, (hydroboost in Anglo-Saxon terminology), it is advantageous to connect the source 116 via a connection 217 to the servomotor 72. However, the implementation of a high pressure source Independent power supply of a hydraulic brake booster does not go beyond the scope of the present invention.

As will be explained in greater detail in relation to Figure 3, it is advantageous not to directly connect the control cylinder chamber 48 connected to the source 116 to the brake fluid reservoir 98. For example, the feedback and / or the evacuation of fluid of brakes of the primary chamber is made by connection 213, source 116 and connection 152 to reservoir 98.

The braking system of Figure 1 requires the implementation of a particularly reliable source 116 to the extent that a leakage through connection 213 would result in the loss of the primary braking circuit. On the contrary, it has the advantage of allowing the evacuation, under control, of the excess brake fluid found in the primary chamber.

The braking system of Figure 2 differs from that illustrated in Figure 1 in that the connection 213 linking a chamber of the control cylinder to the source 116 flows into the feedback chamber between two cup joints resting on the primary piston 207 and also connected by gravitational flow to the reservoir 98 of brake fluid. In such a case, an electrovalve (solenoid) 103 is provided which ensures the hermetic isolation, under control, of the feedback of the feedback chamber of the primary chamber of the control cylinder 48 with respect to the reservoir.

98.

Indeed, source 116 injects brake fluid under pressure into the feedback chamber that is attached to the brake fluid reservoir 98 at atmospheric pressure. The solenoid valve 103, preferably controlled by the computer 5, prevents the return of the pressurized fluid in the tank. On the contrary, the pressurized fluid folds the cup seal forward and allows the primary chamber of the control cylinder 48 to be fed back. However, connection 213 no longer allows a surplus of liquid to be evacuated from the primary chamber of the control cylinder 48, excess that is evacuated to the tank 98 when the piston 207 has receded so that the feedback hole of said piston 207 flows into the feedback chamber.

It should be noted that a leak in connection 213, during braking, does not reduce the pressure in the primary chamber of the control cylinder. However, in the long run, such a leak could cause a decrease in level in the brake fluid reservoir 98.

A connection 213 ensures the supply of pressurized fluid, preferably pressurized brake fluid, of the control cylinder chamber 48 from the pressure source 116 which is equipped with mobile fluid pressurization elements preferably driven directly or indirectly by a motor 88, preferably an electric motor. The source 116 preferably comprises a pump, preferably a piston pump, even preferably consisting of an odd number of pistons for example equal to three or five. Pressurization means can be connected directly to connection 213; in this case, the increase in pressure in this chamber is obtained by the start-up of the pressurization means of the source 116. Alternatively, the source 116 stores pressurized fluid and includes hermetic isolation means, preferably at least one solenoid valve, for supply, in this way, to a pressurized fluid signal 100 to the primary chamber of the control cylinder 48.

Also, it may be advantageous to have hermetic isolation means, under control, external to the source 116 such as the solenoid valve 94 of Figure 2.

In addition, the solenoid valve 94, or the internal hermetic isolation means of the source 116 makes it possible to avoid having to operate the pressure generating means of the source 116 when it is not necessary, for example during constant level braking.

In the preferred example illustrated, the braking system includes a sensor 66, preferably a position sensor, more preferably a relative position sensor of a first mobile element attached to the brake pedal 1, relative to the position of a second mobile element connected. to a piston 78 that ensures braking assistance. It is understood that other sensors can be implemented such as an absolute position sensor of the control rod 36, a gauge of the deformation of the force exerted on this rod, a pressure sensor existing in the braking circuits and / or at the level of source 116, or others. In the preferred example illustrated, the sensor 66 emits a signal 65 to a computer 5 (ECU or Electronic Control Unit in Anglo-Saxon terminology) which in turn emits a control signal 100 to the pressure source 116. Preferably, the computer 5 includes a pressure source control program 116 based on the relative positions of the two moving elements, the equilibrium position requested by the setpoints of the computer 5 which can be zero or preferably correspond to a lag in order to, as shown symbolically in figure 4 by points 15.1, 15.2,

17.1 and 17.2, dynamically, under control, increase or decrease jumps during braking.

In Figure 3, an example of an embodiment of a servomotor according to the present invention can be seen, associated, in the front part, with a control cylinder 48, preferably a tandem control cylinder. Preferably, the servomotor includes a substantially tubular body 201, whose front part 203 receives the rear part of the control cylinder 48 by, for example, a fastening by bolts (not shown) that pass through openings arranged in flanges or the like. It is preferable to be able to use standard control cylinders, or at most slightly modified with respect to standard control cylinders, normally used with pneumatic brake booster servomotors. The back 205 includes a fixing flange on the vehicle dashboard. Inside a mechanized bore of the body 201, a hydraulic piston 78 is provided which defines with said bore a thrust chamber 76. Preferably, the servomotor according to the present invention is equipped with a reaction device, such as a disk of reaction 40 arranged, in the illustrated example, in a housing of the piston 78, housing whose rear face forms a support parapet on the rear face of the disk 40 and which has a central receiving opening of a piston 32. The surface relationship between the one of the parapet of the pneumatic piston and the one of the frontal face of the piston 32 capable of resting on the rear face of the disk 40 determines the assistance ratio of the servomotor. A resting distance between the front face of the plunger and the rear face, facing each other with the reaction disk, measured according to the servo motor-drive cylinder coupling axis, determines the jump. A pushrod 47 rests on a front face of the reaction disc 40 and on the rear of a primary piston 207 of the control cylinder. A return spring 209, preferably helical, ensures the return of the hydraulic piston 78 to its rest position. Also, a return spring 211, of lower stiffness, returns the piston 32 to its resting position. A control rod 36 receives the thrust of a brake pedal 1 that transmits to the piston 32.

The servomotor of Figure 3 provides great operational safety insofar as in the event of a failure of the source 116, only the return spring 209 opposes braking (not assisted) allowing a damaged vehicle to stop. The force to be exerted, especially in this case, can still be limited by choosing a smaller diameter for at least one of the drills of the control cylinder 48.

In Fig. 3, an embodiment example of a servomotor according to the present invention can be seen in which the pressure source 116 includes a pump 215 driven by an electric motor 88. Preferably, the source 116 includes airtight isolation means 118, preferably under control of the computer 5, of the supply connection 213 of the thrust chamber 76. In the example illustrated in Figure 3, the hermetic isolation means 118 includes a first solenoid solenoid valve 118.1 which ensures, under control, during a braking or a decrease in braking, the return of the brake fluid to a reservoir 98 of brake fluid. The return is carried out, for example, by a conduit 152 that links the output of the solenoid solenoid valve 118.1 with the low pressure aspiration of the pump 215 to the reservoir 98.

On the other hand, the tank 98 ensures by gravitational flow the supply of the control cylinder 48 with brake fluid at atmospheric pressure.

Preferably, the hermetic isolation means also include an electromagnetic solenoid valve 118.2, which links, under control, preferably from the computer 5, the high pressure drive of the pump 215 to the connection 213 of the thrust chamber 76. Although the implementation of the proportional solenoid solenoid valve does not depart from the scope of the present invention, the solenoid solenoid valves implemented in the different variants of the servomotor according to the present invention preferably implement solenoid solenoid valves that operate all or nothing preferably governed by pulse amplitude modulation (Press Width Modulation, PWM, in Anglo-Saxon terminology).

Preferably, the pressure source 116 includes, connected to the high pressure drive of the pump 215, a pressure brake fluid accumulator 148, allowing the engine 88 of the pump 215 not to be started more than when necessary, by For example, when the pressure at the pump 215 of the accumulator 148 is lower than a desired low pressure threshold detected for example by a pressure sensor 150.

When the driver rests his foot on the pedal 1, on the one hand he drives the control rod 36, the piston 32, the reaction disk 40, the push rod 47 and the primary piston 207 of the control cylinder. The increase in pressure in the primary chamber ensures the displacement of the secondary piston of the control cylinder 48. On the other hand, the brake setpoint is detected by a sensor, for example the sensor 66 that sends a signal to the computer 5 that ensures the supply of pressurized fluid, from the source 116 of the thrust chamber 76, simultaneously ensuring braking assistance. On the other hand, the computer 5 can receive by means of a connection 19 complementary information from other sensors and / or computers of the vehicle. For example, you can receive an automatic braking order without support from the driver on pedal 1. This braking is also done by feeding pressurized fluid through connection 213 of chamber 76. It should be noted that in the example illustrated in figure 2, the brake pedal 1 sinks during automatic braking.

Preferably, at least certain source 116 devices are used to ensure brake modulation and especially anti-lock wheels (ABS), adhesion control (ASR), path control (ESP) or others. The implementation of the pump 215, of the engine 88, of the sensor 150, and possibly of the accumulator 148 and the common hermetic isolation means 118 allows to reduce the cost price of the braking system of the vehicle and / or offer additional functions with an increase of Moderate costs

Preferably, the hermetic isolation means 118 of the source 116 further include a third solenoid valve 118.3, which links, under the control of the computer 5, the high pressure drive of the pump 215, the accumulator 148 and / or the solenoid valve 118.2 to a of the chambers of the control cylinder 48, for example, as illustrated, to the primary chamber of said control cylinder 48. In a first variant embodiment, a supply conduit 217, under control, of the primary chamber of the cylinder of command flows into a feedback chamber of the control cylinder disposed between two cup seals installed on the primary piston 207. In this case, a leak at the level of valves 118.3 and 118.1 does not compromise the braking safety to the extent that the Cup seals oppose a decrease in pressure in the control cylinder chamber. However, in such a case, it is necessary to ensure the hermetic isolation of the feedback chamber with respect to the reservoir 98 in order to prevent the introduction of pressurized brake fluid into this reservoir. In a first variant, illustrated in Figures 2 and 4, there is a supplementary solenoid valve 103 located in the supply connection of the control cylinder chamber and reservoir 98. In the preferred example illustrated, the direct connection is simply suppressed between the reservoir 98 and the feedback chamber / primary chamber of the control cylinder 48. In fact, the feedback and returns to the reservoir 98 of the brake fluid are carried out by conduction 217, solenoid valve 118.3, solenoid valve 118.1 and conduction 152.

Preferably, the effective surface of the thrust chamber 76 is adapted to the effective surface of the primary and / or secondary piston of the control cylinder 48.

For example, the effective area of the thrust chamber 76 with respect to that of the control cylinder chambers is increased if a weak pressure (for example limited to 107 Pa) of the source of pressurized brake fluid is to be compensated. However, such a surface relationship runs the risk of inducing a movement of the brake pedal 1 during active modes.

For said equal surfaces, the saturation pressure, that is to say the maximum pressure provided by the high pressure source is equal to the pressure generated by the output assistance of the control cylinder. Pedal 1 remains motionless during active modes.

For effective surfaces of the thrust chamber 76 lower than those of the pistons of the control cylinder, the volume of fluid to be provided to the chamber 76 for a given braking is reduced, which allows to limit the flow of the pump, decrease the volume of the accumulator and / or improve braking dynamics, that is, reduce the response time of the braking system.

In the illustrated example, in Figure 4, the supply pressure pressure source 116 of the thrust chamber 76 includes a control cylinder 82 that includes a variable volume chamber 84 in which the brake fluid pressure is increased by a piston 86 driven, under control 100 by a motor 88, preferably an electric motor.

In the illustrated example, in Figure 4, the chamber 84 is an annular chamber connected by a line 90 to the thrust chamber 76. Preferably, the motor is a stepper motor and drives the piston 86 by means of a spindle balls.

In the preferred example illustrated, the piston 86 includes at least one of its axial ends, a hydraulic seal capable of withstanding the control pressures, preferably, as illustrated, a cup-shaped seal.

Preferably, the servomotor according to the present invention further includes an electrovalve 94 that ensures the hermetic closure, under control, of a conduit 96 that joins the chamber 84 to the control cylinder 48. In the preferred example illustrated, the conduit 96 flows through the side of the control cylinder 48 between two cup joints defining, in a known way, a feedback chamber of the control cylinder. This chamber is also attached to a reservoir 98 of brake fluid. Furthermore, at rest, the feedback chamber joins through the openings made in the primary piston to the primary chamber of the control cylinder 48. On the contrary, when the primary piston advances, the openings pass beyond the gasket. anterior cup allowing the pressure rise of the braking circuit. The solenoid valve 94 allows, in the event of a breakdown of the engine 88 during braking, to release the pressure of the chamber 84 in the tank 98 and thus avoid, in the event of a failure of the engine 88, unwanted braking. Similarly, it should be noted that in the absence of assistance after a failure of the motor 88, a push on the control rod directly drives the push rod 47 without having to drive the motor 88.

Preferably, the servomotor according to the present invention includes a second isolation solenoid valve 102, under control of the thrust chamber 76 of the chamber 84 of the control cylinder 82. Thus, it is possible to maintain a constant hydraulic brake pressure regardless of the action of the engine. This can be useful, for example, for constant pressures on the brake pedal, for example during a stop at a traffic light, a prolonged stop or a descent on a steep road with constant braking. Therefore, it is not useful in such a case to drive the motor 88. This reduces both the electrical consumption and the wear of the motor. The second solenoid valve 102 is especially useful in the case of the installation of reversible spindles, that is spindles that can be rotated by a variation of pressure in the motor chamber 76.

Preferably, the servomotor according to the present invention further includes a third solenoid solenoid valve 103, under control, of the primary chamber of the control cylinder 48 of the brake fluid reservoir 98. Thus it is possible to ensure the previous filling of the braking circuit through the control cylinder by opening the solenoid solenoid valve 94 and closing the solenoid valve 103 in order to prevent the pressure provided to the primary chamber from escaping into the reservoir. It should be noted that the previous filling of the brakes is carried out without the advancement of the control rod 36, as a result of the brake pedal 1. Similarly, the combination of the solenoid valve 94 open and the solenoid solenoid valve 103 closed, allows to implement active braking modes, that is under the control of computer 5, without the need for driver action and without pedal displacement 1. It should be noted that the secondary piston transmits the pressure in the primary chamber to the secondary chamber, especially during braking assets.

Pre-filling the brake can be very useful to reduce braking distances and / or to allow

implementation of the hydraulic brake with greater piston recoil that has a residual braking torque (no

desired) null and / or at least reduced.

Furthermore, the solenoid valve 103 or other hermetic isolation means, under control, can be operated to isolate at least one of the control cylinder chambers 48, usually the primary chamber in order, for example, to reduce the neutral path at the time. of actuating the brakes, and preferably before the feedback holes of the primary piston have passed the front cup seal of the primary chamber of the control cylinder or, if an abnormally high temperature has been detected during braking with the risk of causing In the event of a decrease in braking, the boiling of the brake fluid. However, during complete braking, that is, without resting on the brake pedal, eventually after a delay, the solenoid solenoid valve 103 is reopened in order to avoid unwanted braking.

In Fig. 5, a preferred example of a servomotor according to the present invention can be seen in which the thrust chamber 76 is fed by a motorized control cylinder 84. In the preferred example, the control cylinder 84 is a tandem control cylinder, illustrated in more detail in Figure 6, whose primary chamber 84.1 feeds the connection 213 of the thrust chamber 76 and whose secondary chamber 84.2 feeds through a connection 217 the primary chamber of the control cylinder 48. It should be noted that in such a case, the feeding is preferably carried out directly in the chamber of the control cylinder and not in the feedback chamber thereof. Preferably, as illustrated, only the secondary chamber of the control cylinder 48 is fed, by gravity, by the reservoir 98 of brake fluid at atmospheric pressure. Preferably, a two-way solenoid valve 219 joins, under control, during braking, the secondary chamber 84.2 of the control cylinder 84 to the primary chamber of the control cylinder 48 feeding the braking circuit. In this position, the solenoid valve 219 simultaneously ensures the hermetic isolation of the conduit 217 of the supply of the primary chamber of the reservoir 48 with respect to the conduit 152 connected to the reservoir 98.

In a second position, without brake, the valve 219 isolates the conduit 217 with respect to the secondary chamber 84.2 of the control cylinder 84 (and with respect to the conduit 152 connected to the tank 98) and connects the conduit 152 to the secondary chamber 84.2 of the cylinder of control 84. Preferably, the connection 152 is also permanently connected to a feedback chamber 221 of the primary chamber 84.1 of the control cylinder 84. Said feedback chamber 221 is confined to a machined bore of the control cylinder 84 by means of two cup seals 223 arranged in the primary part of the piston 86. Said piston 86 includes feedback holes 225 preferably arranged radially in order to communicate, at rest, that is, when the piston recoils to the maximum (towards on the right of figure 6), the primary chamber 84.1 of the control cylinder 84 with the conduit 152 attached to the tank 98. The piston advance 86 deploys aza the feedback holes 125 that pass beyond the previous cup seal 123 which at that time ensures the isolation of the conduit 152 with respect to the primary chamber 84.1.

Preferably, the machined holes of the primary chambers 84.1 and secondary chambers 84.2 of the control cylinder 84 have different diameters. Preferably, the diameter of the secondary chamber 84.2 is smaller than the diameter of the primary chamber 84.1. So:

With the solenoid valve 119 not activated, the actuation of the brake pedal causes a displacement of the hydraulic fluid from the primary chamber of the control cylinder 84 towards the working chamber 76 according to the signal of the control device. Simultaneously, the volume displaced by the chamber Secondary of this same control cylinder will be transferred to the tank without raising the pressure through solenoid valve 219 and conduction 152. This last fluid displacement will therefore not influence the braking characteristic. The relationship between the input path of the control rod 36 and the pressure of the primary and secondary chambers of the control cylinder 48 will therefore be a function of the respective sections of the chambers of this last control cylinder, and of the vehicle braking receivers (brakes), as for conventional braking systems called "uncoupled".

With the solenoid valve 119 activated, due to the total separation of the two chambers of the control cylinder 84, the actuation of the brake pedal causes a simultaneous displacement of hydraulic fluid from the primary chamber of the control cylinder 84 according to the signal of the control device. towards the working chamber 76, and from the secondary chamber of this last control cylinder towards the primary chamber of the control cylinder 48. The value of this last volume of fluid will be a function of the section of the secondary chamber of the control cylinder 84 This additional volume with respect to the braking situation described in the preceding paragraph participates in the filling of the primary and secondary braking circuits of the vehicle. Consequently, the input stroke of the control rod 36 necessary to reach a given brake circuit pressure will be reduced by a value proportional to the section of the secondary chamber of the control cylinder 84. It is possible with a braking system called no decoupled and that offers advantages in terms of robustness and pedal sensation with respect to a system called “decoupled” with simulator, to obtain a braking characteristic inlet path / shorter circuit pressure, keeping a control cylinder 48 dimensioned in a conventional way in order to achieve emergency braking benefits (in case of breakdown of brake assistance) required by law.

Conversely, a vehicle that has an electronic system of the HBC type, that is, with pressure generation by means of the hydraulic group of the ESP device to compensate for an eventual failure of the braking assistance to respond to the legislation in the sense of being able to maintain An acceptable pedal travel in the normal braking mode can benefit from the invention by increasing the robustness. Thus, for example, a breakdown of the total electric current of the vehicle will not influence the emergency braking performance, contrary to the case in which the vehicle has an electronic function to reach the braking distance required by law.

On the other hand, this device can be marketed as a function that allows the driver to choose between two braking system behaviors. The choice is made through a user interface, for example, by pressing a control button or by choosing from a vehicle configuration menu. For example, a "normal" mode for which the solenoid valve 119 would be in the non-activated position, and a "sporty" mode for which the solenoid valve 119 would be activated, thus offering the driver a shorter travel pedal and better adapted to a sports driving

Preferably, a single piston 86 between two mechanically joined pistons in translation along the axis of the control cylinder 84 ensures the pressurization of the brake fluid present in the chambers 84.1 and 84.2. In the preferred example illustrated, the single piston 86 includes a rear tubular area 86.1 in which the cup joints 223 extended forward to the chamber 84.2 are installed by means of a coaxial rod 86.2 terminated on a disk 86.3 forming a secondary piston provided with a slot for receiving a seal 225 for example O-ring.

The piston 86 allows feeding the control cylinder chamber 48 as well as the thrust chamber 76 but also the Length and diameter of the pistons allow to select the volumes to be injected. The invention is especially applied in the automobile industry. The invention is mainly applied in the brake industry.

(5)

 Computer

(19)

 Signal

(32)

 Plunger

(36)

 Control rod

(40)

 Reaction disk

(47)

 Pushrod

(48)

 Control cylinder

(65)

 Brake setpoints

(66)

 Sensor

(72)

 Brake assist servo motor

(76)

 Thrust chamber

(78)

 Piston

(84)

 Camera

(86)

 Piston

(88)

 Engine

(90)

 Driving

(94)

 Solenoid valve

(96)

 Driving

(98)

 Brake fluid reservoir

(100) Command signal

(103) Solenoid valve

(116) Source

(118) Medium (thermal insulation)

(148) Accumulator

(150) Pressure sensor

(152) Union

(201) Body

(203) Front

(205) Rear

(207) Primary Piston

(209) Return spring

(211) Return spring

(213) Connection

(215) Bomb

(217) Connection

(221) Feedback Camera

(223) Cup seals

(225) Feedback Holes

Claims (8)

1.-Control cylinder (48) that includes at least one variable volume chamber and a mobile piston (207), whose displacement causes the volume of said chamber to vary, means for connecting said chamber to a hydraulic circuit of braking and connection means (217) to a source (116) of pressurized brake fluid comprising a control cylinder that includes a first chamber (84.2) of variable volume and a piston (86), said chamber being connected by connection means (217) to said chamber of said control cylinder (48) including connection means to a hydraulic circuit, and a second chamber of variable volume (84.1) connected by a connection (213) to said assistance means hydraulic braking (76), characterized in that the piston (86) is driven, under the control of a computer (5), by a motor (88). 2.-Control cylinder according to claim 1, characterized in that said means (217) for connection to a source (116) of pressurized brake fluid flow directly into said variable volume chamber. 3.-Control cylinder according to claim 1, characterized in that it includes a feedback chamber and that said means (217) for connecting to a source of high-pressure brake fluid flow into said feedback chamber. 4. Braking system characterized in that it includes a control cylinder according to any one of the preceding claims, a source (116) of pressurized brake fluid connected by said connection means (217) to said variable volume chamber of the said control cylinder (48) and control means (5, 219, 118) for supplying said variable volume chamber with pressurized brake fluid. 5.-Braking system according to claim 4, characterized in that it also includes hydraulic braking assistance means (76). 6. - Braking system according to claim 5, characterized in that it includes means (213) for connecting the source of pressurized brake fluid (116) to a thrust chamber (76) of said hydraulic braking assistance means. 7. Braking system according to claim 4, 5 or 6, characterized in that it also includes means (118, 219) of hermetic isolation, under control, of said variable volume chamber of said control cylinder (48) with respect to the said source (116) of pressurized brake fluid. 8. Braking system according to claim 1, characterized in that said control cylinder (82) of said source (116) of pressurized brake fluid includes two chambers (84.2, 84.1) that have two different diameters and why these they include means (86.2) that join in translation the means (86.3, 86.1) that ensure the variation of the internal volumes of said variable volume chambers (84.2, 84.1) of said control cylinder.